Activities of aluminum-26 and beryllium-10 in marine sediment were measured at 0.01 +/- 0.13 and 4.4 +/- 0.9 disintegrations per minute, per kilogram dry weight, respectively. Only an upper limit of 0.03 could be determined for the ratio of aluminum-26 to beryllium-10 in the sediment. The ratio is probably explained by production by cosmic rays in the atmosphere.